使用Transformer时Hibernate异常PropertyNotFoundException

Question

我正在使用hibernate和hql来查询我的Java代码.但我得到了这样的例外:

Caused by: org.hibernate.PropertyNotFoundException: Could not find setter for 0 on class [my class]
    at org.hibernate.property.ChainedPropertyAccessor.getSetter(ChainedPropertyAccessor.java:44)

我不明白"0"是什么意思.以下是一些带有示例的deatils:

我有几个表加入hql.表格如下:

A
- A_ID
- NAME

B
- B_ID
- A_ID

C
- C_ID
- B_ID
- LENGTH
- UNIT

类别:

@Entity
@Table(name="A")
class A
{
    @Id
    @Column(name="A_ID", updatable=false)
    private Long id;

    @Column(name="NAME", nullable=false, length=10, updatable=false)
    private String name;

    @OneToMany(mappedBy="a", fetch=FetchType.LAZY, cascade={CascadeType.ALL})
    @JoinColumn(name="A_ID", nullable=false)
    private Set<B> bs;

    @Transient
    private Double length;

    @Transient
    private String unit;

    // Setters and getters
    ...
}

@Entity
@Table(name="B")
class B
{
    @Id
    @Column(name="B_ID", updatable=false)
    private Long id;

    @ManyToOne
    @JoinColumn(name="A_ID", nullable=false, insertable=true, updatable=false)
    private A a;

    @OneToMany(mappedBy="b", fetch=FetchType.LAZY, cascade={CascadeType.ALL})
    @JoinColumn(name="B_ID", nullable=false)
    private Set<C> cs;

    // Setters and getters
    ...
}

@Entity
@Table(name="C")
class C
{
    @Id
    @Column(name="C_ID", updatable=false)
    private Long id;

    @ManyToOne
    @JoinColumn(name="B_ID", nullable=false, insertable=true, updatable=false)
    private B b;

    @Column(name="LENGTH", nullable=false, updatable=false)
    private Double length;

    @Column(name="UNIT", nullable=false, length=10, updatable=false)
    private String unit;

    // Setters and getters
    ...
}

HQL:

select a, sum(c.length) as length, min(c.unit) as unit
from A a
left outer join a.b as b
left outer join b.c as c
group by
a.id
a.name

查询:

Query query = session.createQuery(hql.toString()).setResultTransformer(Transformers.aliasToBean(A.class));

结果是一个对象"A"的列表,其中收集了长度和单位.我不明白为什么我得到这个例外.请给出一些建议.

---

更新:

我写了一个ResultTransformer并输出所有"别名"来查看问题:

-> 0
-> length
-> unit

它似乎除了长度和单位之外还对待"A".我的HQL应该有一些问题吗？

Answer 1

发现问题:

即使HQL可以正确转换为sql,但是当ResultTransformer获得结果时,结果中只有3个字段:

1. A
2. length
3. unit

无论A中有多少个字段,它们都会聚合到一个字段"A"中,因为我没有为该字段设置任何别名,所以它将被视为"字段0".

所以我改变了HQL之后解决了这个问题:

select a.id as id, a.name as name, sum(c.length) as length, min(c.unit) as unit
from A a
left outer join a.b as b
left outer join b.c as c
group by
a.id
a.name